UPDATE 838939 <- Should be no-change
DELETE 838939 <- Should be no-change. Also, key not repeated.
UPDATE 4700943 <- Should be INSERT
INSERT 536636 <- Should be no-change
And missing a 'DELETE 4672156'

Problem #2:
- when hash collisions do occur, lines 2227/2252/2272 all try to do comparisons (eq, lt, gt) on arrays, which perl doesn't support. It compares the lengths, which are always true.

(also, is it possible to put the source code on github/bitbucket/somewhere? Makes it vastly easier to analyse changes, contribute improvements, and improve the test coverage. And the bug tracker is 100x nicer to use!)